Leviticus 23:20 - Matthew Poole's English Annotations on the Holy Bible

The priest shall wave them, i.e. some part of them in the name of the whole, and so for the two lambs, otherwise they had been too big and too heavy to be waved. So it is a synecdochical expression. For the priests; who had to themselves not only the breast and shoulder, as in others, which belonged to the priest, but also the rest which belonged to the offerer, because the whole congregation being the offerer here, it could neither be distributed to them all, nor given to some without offence or injury to the rest.